Device in connection with diaphragm carburettor

ABSTRACT

In an internal combustion engine diaphgram carburetor having a liquid fuel inlet valve controlled by a diaphgram and a choke valve in the fuel mixture duct, a device operated by said choke valve in its choking or hot start position, pressing against said diaphragm to open said inlet valve.

United States Patent [191 Wildt-Persson et al.

[ Nov. 18, 1975 DEVICE IN CONNECTION WITH DIAPHRAGM CARBURETTOR [76] Inventors: Fredrik Wildt-Persson, Taledsvagen 13, 43600 Askim; Billy Nicklasson,

Botekullsg 24, 41475 Goteborg, both of Sweden 22 Filed: Oct.ll, 1973 21 Appl. No.: 405,855

[30] Foreign Application Priority Data Oct. 24,1972 Sweden 13696/72 [52] US. Cl 261/35; 261/35; 261/50 R; 261/DlG. 73

[51] Int. Cl. F02M 17/04; F02M l/lO [58] Field of Search 261/DIG. 68, 35, 50 R, 26l/DlG. 73; 123/119 F, 187.5 R

['56] References Cited UNITED STATES PATENTS 1,728,730 9/1929 Grisdalla. 261/50 R 2,392,055 l/1946 Mennesson 261/50 R 2,728,564 12/1955 Bracke 261/DlG. 68 3,037,751 6/1962 Phillips 261/D1G. 68 3,227,428 l/l966 Charron.... 261/39 C 3/1968 Turner 26 1/DIG. 68

Primary ExaminerTim R. Miles Attorney, Agent, or Firm-Ulle C. Linton [57] ABSTRACT In, an internal combustion engine diaphgram carburetor having a liquid fuel inlet valve controlled by a diaphgram and a choke valve in the fuel mixture duct, a device operated by said choke valve in its choking or hot start position, pressing'against said diaphragm to open said inlet valve.

3 Claims, 2 Drawing Figures US. Patent Nov. 18, 1975 FIG. I

DEVICE IN CONNECTION DIAPHRAGM CARBURETTOR The present invention relates to a device in connection with diaphragm carburettors for opening the fuel inlet valve thereof at times of cold or hot starting of the engine.

In connection with combustion engines diaphragm carburettors are sometimes used in order to create the required mixture of air and fuel. Such carburettors have the shape of a unit, which in addition to the carburettor itself comprising an air passage duct suitably shaped for the purpose, in which duct nozzles for fuel have their orifices, usually also comprise a throttle for regulation of the air flow, another throttle to permit choking at low temperatures and further a regulating mechanism for the supply of fuel to the nozzles. The regulating mechanism comprises a regulating valve, which controls the flow to a fuel chamber located before the nozzles as seen in the direction of flow, said valve either being controlled by a float located in the chamber or by a diaphragm separating the chamber from the surrounding air. According to their design such carburettor units generally are denominated float carburettors and diaphragm carburettors respectively. In addition the carburettor unit may comprise a fuel pump, which especially is the case in connection with small diaphragm carburettors for portable tools driven by combustion engines, by way of example motor saws, and the unit is of course also provided with the necessary channels of connection between its different parts. In such carburettor units vapor bubbles are easily created in the fuel during pauses in the operation when the engine is hot and the flow of coolant and fuel ceases. In float carburettors the vaporized fuel has a possibility to escape through the float chamber, but this possibility does not exist in diaphragm carburettors, where the diaphragm chamber is closed having no openings for evacuation and moreover the regulating valve is spring loaded. By this arrangement it is difficult or impossible to start the engine as long as it is hot. In connection with diaphragm carburettor units which as mentioned above are especially used in connection with combustion engine driven portable tools, which shall work in all positions, the problem is aggrevated by the fact that such tools mostly are of a compact design, whereby the carburettor unit is exposed to strong heating.

It is an object of the present invention to solve the above mentioned problems and provide a possibility of escape for the evaporated fuel. When solving this problem, one made it a condition that the engine should not have to be provided with any extra regulation means, which only would make the same more expensive and complicate its operation.

The object of the invention was reached by designing the device for the carburettor unit according to what is indicated at the characterizing part of claim 1.

In the accompanying drawing, an embodiment of a device according to the invention is illustrated.

FIG. 1 shows a diaphragm carburettor unit in a partly broken central cross sectional view, while FIG. 2 illustrates the same carburettor unit in a front view on a somewhat smaller scale.

According to the figures the carburettor unit comprises a housing 1 with end walls 2 and 3 and a duct 4 extending between said end walls. A gas throttle 6 which can be pivoted together with a shaft is inserted in the duct 4, in which also a choke throttle 8 with a hole 9 likewise pivotable together with a shaft 7 is inserted. diaphragm pump with a pump diaphragm 10 is incorporated into the housing 1 above the duct 4, and the same is the case with a pump chamber 11, two flap valves 12, an input channel 13 for the fuel and an output channel 14 for the fuel (the channel 14 is illustrated in FIG. 1 in a cross section, which has been broken and extends in front "of the duct 4). Opposite the pump chamber 11 on the other side of the diaphragm 10 there is a chamber 15 provided with a channel 16 debouching in the end wall 3.

The output channel 14 from the diaphragm pump debouches via a valve 17 into a chamber 18, which is closed by means of a diaphragm 19, the side of which turning away from the chamber 18 faces a compartment 20, which via a hole 21 communicates with the surrounding atmosphere. Via a short bar 22 shaped like a rivet and fastened to the diaphragm l9, and a'doublearmed lever 24 journalled around an axis 23v the valve 17 is in connection with the diaphragm. A spring 25 tends to keep the valve 17 closed, at the same time biassing the diaphragm 19 in outwards direction towards the compartment 20.

The diaphragm chamber 18 via channels and bores, filtering elements and adjustable needle valves 26 debouches via nozzle bores 27 in the duct 4 of the carburettor.

On the shaft 7 of the choke throttle 8 an operating arm 28 with a first hole 29 and a second hole 30 is attached, a stiff wire 31 being led through said last mentioned hole 30 (for the sake of clarity the wire 31 is broken in FIG. 1, compare FIG. 2). As is evident from FIG. 2 the wire 31 via a portion bent in an angle passes to a spirally wound portion 32, from which via a second straight portion 33 it passes to an inwards bent end portion 34 located right in front of the outer end of the bar/rivet 22 of the diaphragm 19.

The shaft 7 of the choke throttle 8 exhibits three setting positions. The first'one, or the operating position, is shown in FIG. 1 and here the choke throttle is completely open, the arm 28 then occupying its top position. The other setting position is illustrated in FIG. 2, and here the choke throttle occupies a totally closed position, the choking position, the arm 28 then being in its bottom position. The third position .is an. intermediate position, the hot start position with the choke throttle 8 halfway open and the arm 28 slightly downwards inclined relative to the position illustrated in FIG. 1. The shape of the wire 31 34 is adjusted in such a manner that in the top position of the arm 28, or the operating position for the choke throttle the end portion 34 has not contact with the bar/rivet 22, so that the diaphragm 19 can work completely free and entirely close the valve 17. In the intermediate position, or the hot start position, the wire 31 has been carried so far downwards that the portion 33 is pressed inwards against the diaphragm 19, so that the end portion 34 presses upon the bar/rivet 22 to such an extent that the lever arm 24 is pivoted and opens the valve 17. Finally, in the choking position the wire 21 is pushed still further downwards, but the portion 33, 34 cannot be pressed inwards much more relative to the hot start position, because of the portion 33 abutting upon the cover defining the compartment 20, causing the wire in the spirally wound portion 32 to spring, so that the movement of the shaft 7 of the choke throttle is not impeded.

The mode of operation of the carburettor unit is in itself well known, but it should anyhow be mentioned, that with the end of the duct 4 where it debouches at the end wall 3, it is connected to the air/fuel input of the engine, while the other end of the duct at the end wall 2 is connected with an air filter. Cl he fuel supply channel 13 is connected with a fuel tank, and the channel 16 is connected with the crankcase of the engine. The shaft 5 of the gas throttle is connected with a gas control and the shaft 7 of the choking throttle via the arm 28 and the hole 29 is connected with a manually operated choking control.

When the engine is in operation a pulsation is transmitted from the crankcase via the channel 16 to the chamber and consequently to the pump diaphragm 10, causing fuel from the channel 13 via the valves 12 and the pump chamber 11 to be pumped out through the channel 14. Via the valve 17, the diaphragm chamber 18, the filters and the needle valves 26 this fuel passes out through the nozzle bores 27 and out into the duct 4 in order to be introduced into the engine together with the air taken in. However, the diaphragm pump tends to pump a greater quantity of fuel than what is required for the operation of the engine, or what is escaping out of the nozzle bores 27. This produces an increase of the pressure in the diaphragm chamber, so that the diaphragm 19 via the bar 22 tends to pull the lever arm 24 outwards and close the valve 17, the spring 25 helping therewith. As soon as the pressure in the diaphragm chamber 18 is reduced by fuel being carried away into the engine, the diaphragm 19 is actuated by the atmospheric pressure in the compartment thereby communicating an opening up movement of the valve 17. In operation this makes the valve adjust itself in a suitable opening position. When the engine is working its number of revolutions is controlled by means of the gas throttle 6 which can be adjusted in different opening positions.

When a cold engine shall be started, the choke throttle 8 is manually adjusted in its closed position shown in FIG. 2, take-in of air then only being possible through the hole 9, whereby the desired greater fuel contents of the air fuel mixture is obtained.

If the engine is stopped when the engine itself and the carburettor unit have been heated up, the fuel in the fuel chamber and channels of the carburettor unit including those in the part, where the pump is located, will boil during the pause and give rise to vapor accumulations. If the engine subsequently is going to be started when it still is hot, there will be difficulties because of the diaphragm pump 'not being able to press in halfway open position by means of the customary choke throttle, in which position the wire 31 is pressed downwards so much that its position 33 is pressed inwards, whereby the end portion 34 presses the bar/rivet 22 inwards, so that the valve 17 is opened up. If the shaft 7 is pivoted a little further to the choking position, a springing action takes place in the spirally wound portion 32, as mentioned above, while the wire portions 33, 34 are stopped by the cover defining the compartment 20, so that any further pressing in of the diaphragm 19 in addition to the earlier mentioned one is not obtained. The valve 17 thus will stand open in the choking position in addition to the hot start position (the intermediate position), which is not of any disadvantage. On the other side in the operating position, i.e. in the completely open position of the choking throttle, the wire 31 is displaced to such an extent in upwards direction that the diaphragm and the valve 17 are not subjected to any bias.

Thus, the device can be set into the hot start position by means of the customary choking throttle. During the course of the starting operation the choking throttle is in such open position that any real choking of the engine cannot take place. Already in this position, however, the valve is in a suitably open position and by the fact that the transmission of movement between the shaft of the choking throttle and the part biassing the diaphragm being made resilient, no further biassing of the valve is taking place, when the choking throttle is changed from its hot start setting into choking position.

We claim:

1. In a diaphragm carburetor having a housing with a fuel mixture duct, liquid fuel chamber with fuel outlet to said duct, liquid fuel inlet valve opening into said chamber, a diaphgram closing one side of said chamber, means operable by said diaphgram for opening and closing said inlet valve, a choke valve mounted in said duct, said housing having an opening adjacent said diaphgram, a link having one end portion pivotally connected to said choke valve and having a resilient intermediate portion pivotally mounted on the exterior of said housing with the other end portion extending through said housing opening beneath said diaphgram whereby movement of said choke valve to its hot start position causes said link other end to move said diaphgram to open said inlet valve.

2. In a diaphgram carburetor as claimed in claim 1 wherein a lever arm is connected to said choke valve and said link one end portion is pivotally connected to said lever arm and said link intermediate portion is a coil of said link and a shaft supported by said housing extends through said coil.

3. In a diaphgram carburetor as claimed in claim 2 wherein said link is a two armed stiff wire with said coil in one arm thereof, said one arm having a bent end extending into said housing opening, and the other arm of said link extending through said lever arm. 

1. IN A DIAPHRAGM CARBURETOR HAVING A HOUSING WITH A FUEL MIXUTE DUCT, LIQUID FUEL CHAMBER WITH FUEL OUTLET TO SAID DUCT LIQUID FUEL INLET VALVE OPENING INTO SAID CHAMBER, A DIAPHGRAM CLOSING ONE SIDE OF SAID CHAMBER, MEANS OPERABLE BY SAID DIAPHGRAM FOR OPENING AND CLOSING SAID INLET VALVE, A CHLKE VALVE MOUNTED IN SAID DUCT, SAID HOUSING HAVING AN OPENING ADJACENT SAID DIAPHGRAM, A LINK HAVING ONE END PORTION PIVOTALLY CONNECTED TO SAID CHOKE VALVE AND HAVING A RESILIENT INTERMEDIATE PORTION PIVOTALLY MOUNTED ON THE EXTERIOR OF SAID HOUSING WITH THE OTHER END PORTION EXTENDING THROUGH SAID HOUSING OPENING BENEATH SAID DIAPHGRAM WHEREBY MOVEMENT OF SAID CHOKE VALVE TO ITS HOT START POSITION CAUSES SAID LINK OTHER END TO MOVE SAID DIAPHGRAM TO OPEN SAID INLET VALVE.
 2. In a diaphgram carburetor as claimed in claim 1 wherein a lever arm is connected to said choke valve and said link one end portion is pivotally connected to said lever arm and said link intermediate portion is a coil of said link and a shaft supported by said housing extends through said coil.
 3. In a diaphgram carburetor as claimed in claim 2 wherein said link is a two armed stiff wire with said coil in one arm thereof, said one arm having a bent end extending into said housing opening, and the other arm of said link extending through said lever arm. 